[Story] Implement per-thread CPU usage panels

[andrewazores]

See cryostatio/cryostat#135 (comment)

Currently, we display some high-level CPU usage or thread activity overview panels:

The jdk.ThreadCPULoad event raw data looks like this in JMC:

While jdk.ObjectAllocationSample looks like this:

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Therefore, it seems reasonable that we could build Grafana panels for jdk.ThreadCPULoad similar to the ones we already have for jdk.ObjectAllocationSample:

The thread load aggregate single panel could add both system mode and user mode load into one value with the thread name as the key, whereas the breakout dashboard would have a panel for each thread name key and a timeseries line for each system mode and user mode load.